Synthesis of new uranium compounds



United States Patent 3,506,410 SYNTHESIS OF NEW URANIUM COMPOUNDS Fritz Hulliger, Zurich, Switzerland, assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Apr. 9, 1968, Ser. No. 719,858

Int. Cl. C01g 1/00 US. Cl. 23-346 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The general process of vapor transport, and particularly halogen vapor transport, is well known. However, as is in all vapor transport reactions, there is no single temperature range, the range depending on the nature of the products produced.

SUMMARY OF THE INVENTION The present invention is directed to new uranium compounds having the formula UXZ, in which X is S, Se, or Te, and YP, As, Sb, or Bi, preferably the compounds are formed as large plate-like single crystals.

The invention also includes a new process of making the compounds from their elements utilizing a modified halogen vapor transport, the transport gas being either elemental halogens Cl, Br, or I or uranium tetra-halide of the formula UHal where Hal can be any of the halogens above referred to. The process is very effective in the case of UPS, UPSe, UAaS, and UAaSe and particularly produces large single crystals.

It has been found that in the process modification of the present invention the high temperature zone is from 1000 to 1200 C., the other end of the transport vessel being from 50 to 100 C. cooler. Larger single crystals are produced in the cooler part with edge lengths up to 10 to mm. and thicknesses ranging from about 0.2 to 1 mm.

The compounds of the present invention in their particular crystalline form are not limited to any single process of formation. Thus powders of mixed UXZ elements may be sintered separately before starting the halogen transport procedure or the elements may be used directly without preliminary sintering. In the latter case, the transport tube, which contains uranium turnings and pieces of the elements X and Z in stoichiometric ratio at one end together with the halogen transport gas or a uranium tetrahalide, is slowly heated to about 800 C. while avoiding a temperature gradient. The tube is kept at this temperature for some hours in order to permit formation of the desired compound in powder form. A temperature gradient is then produced having the gradient set out above.

The single crystals produced vary in color, for example white for USbTe, and have a metallic appearance. The crystal structure is of the same type as PbFCl, and when the crystals are colored they are usually brass colored. At room temperature the single crystals are paramagnetic but become ferromagnetic below about 100 K. Curie points vary somewhat from compound to compound.

It is an advantage that exact proportions of the reacting uranium and other compounds are not too critical. Ordinarily the uranium should be in a small excess because having more uranium will merely speed up the reactions but will not change the nature of the compound produced. However, the ratio X:Z should be equal to one, since otherwise the UXZ crystals are intergrown with crystals of UX or U Y or even U2 Excess arsenic and antimony may condense in elemental form. Usually the excess of uranium is very small and the ratio is substantially stoichiometric corresponding to 10 to 3X10" mole of UXY. In the case of UAsS the composition of the single crystals on checking by electron beam microanalysis was found to correspond exactly to the formula given.

The nature of the transport reaction is determined by the therrno-dynamic considerations of the reacting materials. In a great many cases the deposition of the transported material is at a cooler part of the equipment or transport path, and that is the case in the present reaction. This invention does not belong to the category represented, for example, by deposition of nickel with a carbon monoxide transport gas where the formation of the nickel carbonyl is at a lower temperature than its decomposition temperature at which metallic nickel is deposited. In the present case the temperatures are not very critical. As in a great many halogen vapor transport process, the temperature at one end of the transport path has to be quite high, frequently above 1000 C. In the present case it has been found that a very suitable temperature for the hot end of the transport zone is about 1000 to 1200 C., and the cooler portion where the large single crystals of the compound UXZ are deposited will be from 50 to C. cooler. These temperatures are not critical and considerable variation can be present. This is a valuable, practical advantage of the process aspect of the present invention as it does not require extremely critical temperature control.

As in most halogen vapor transport processes, the concentration of the transporting vapor is comparatively small. In the present case a suitable desirable range is from 10 to 10" gram equivalents/cm? which corresponds to 1.313 mg. iodine/cm. 0.8 mg. bromine/cm. 0.35- 3.5 mg. chlorine/emf. Again, this is not critical and the possibility of using the process without extremely critical control of this factor is a desirable feature.

In modification of the process starting from the elements themselves it is advantageous to cause them to react at lower temperatures, for example below 800 C., without any temperature gradient or even with a small gradient in the reverse direction. The temperature is not raised to the higher point of l000 to 1200 C. until after the desired compound has formed. The other end of the transport vessel is kept 50 to 100 C. cooler.

As the compounds are new compounds, this aspect of the invention is not limited to any process and includes them regardless of the process by which they are formed. While it is possible to produce the compounds from powders, this presents some operating problems as uranium powder is neither easy to handle nor readily available. Therefore, it is preferred to use uranium turnings instead. This results in a smaller surface of uranium exposed to the reaction than would be the case with a powder, and so it takes a somewhat longer time to complete the reaction. Some speeding up of the reaction can be effected by shaking the reaction tube, which appears to remove layers of UXZ formed on the surface of the turnings. Alternatively, UXZ compounds may be prepared by sintering pressed mixtures of UX and U2 powders or U2 and X or UX and Z. The halogen vapor transport, however, is so efiicient that the process feature is important and is included in a preferred modification of the invention. The crystals produced are single crystals and are quite large, for example 10 to 15 mm. edge length and from about 0.2 to 1 mm. thickness. Larger crystals are metallic in appearance and brass to white colored as X, Z vary from light elements (S, Se, P, As) to heavier elements (Te, Sb, Bi) the brass color becomes more and more white. They have a crystal structure of the tetragonal PbFCl type and are semimetallic with resistivities of about 10 ohm cm. at room temperature.

gas back to the hot end. Within one week single crystals of UAsS are formed in the cooler part of the tube. These crystals normally are square with edge lengths up to 5-10 mm. and a thickness of 0.2-0.5 mm.

After formation of the single crystals is substantially As an example, the resistivity of UAsSe crystals has a 5 complete, the tube is slowly cooled down, opened, and the value of 5X10 ohm cm. at 300 K. and a small but UAsS single crystals removed. Excess uranium and uranegative temperature coefficient between 100 and 700 K. nium tetrachloride may be recovered by conventional The crystals are paramagnetic of the Curie-Weiss type. At means and can be reused. The deposit consists of brass a lower temperature the slope of the curve l/ vs. T becolored, metallic, plate-like crystals having a PbFCl struccomes steeper and below about 100 K. the compounds ture with lattice constants as listed in the table. The crysare ferromagnetic. The exact point where the magnetic tals are paramagnetic at room temperature and become transition takes place will vary, of course, somewhat with ferromagnetic below their Curie point of 120 K.

the diiferent compounds, as can be seen from the Table Example 2 which follows the speclfic examples and summarizes data from them. For example, the compounds UAsS has a The procedure is repeated with uranium tetrabrornide C i point near 120 K. Since the crystals are tetragonal, or AsBr or elemental Br. The same product 1s obtalned, their physical properties are anisotropic and they are usehavlhg the Same erySta-lhhe and maghetle chareeteflstlcsful for processes and equiprlnent vghefre these chtaracteris- Example 3 tics are desirable, particu ar y in t e erromagne 1c range.

In the process aspect of the present invention it is an The procedure of Example 1 is repeated, replacing the advantage that quartz tubes or quartblined tubes may be uranium tetrachloride with uranium tetraiodide or eleused No coating with a protecting film is necessary at mental iodlne; The Same pFoducts, ebtalnedz and the the t'emperatures used for UPS UPSe, and UAsS and transport is sllghtly faster with the iodine-contalnlng trans- UAsSe, which is a further operating advantage. However, P The y h are also larger, edge lengths of in the case of compounds which do not form easily, for 15 and thlekheSS 0f mm. are normal. example USbS, USbSe and USbTe, reaction with silica Exampla 4 may prevent formation of the desired compound. Sma The d proce ure of Example 3 was repeated, replacing the smglgdcrystatls tofbthese Compounds can be grown 1n carbon sulfur with selenium. Single crystals of UAsSe were procoat quar Z u duced and had similar physical characteristics, especially DESCRIPTION OF THE PREFERRED similar magnetic characteristics to the products of Exam- EMBODIMENTS p b d t th th Example 5 'unc ion wi e i g gzg ggg g if gzz e m con] The procedure of Example 3 was repeated, replacing the arsenic with a corresponding amount of phosphorus. Example 1 The single crystals of UPS were produced and were similar in their chemical and physical characteristics, includ- A slight excess of uranium turnmgs and pieces of arsenic ing magnetic characteristics, to those of Example and sulfur in amount corresponding to about 2 10 40 mole of the final UAsS compound are placed in one end Example 5 of a closed quartz tube of 25-40 mm. diameter with a Th procedure f Example 4 was repeated, replacing length of and a Wall thlckhess of 2 the arsenic with a corresponding amount of phosphorus. m T t 18 llneoatefl of y be eerhoh'eeated oh'lts The crystals obtained of UPSe were similar in their cheminsld T quartz tube 18 evacuated, filled Wlth ehlorlhe ical and physical characteristics, including magnetic chargas in an amount of mg/eIh-Ef of the tuhevohlme, h acteristics, to the produce of Example 4. As in the case then cl S A Ye y ehlol'lhe y be Introduced 111 of all of the preceding examples, at low temperatures the th form of the reqlllslte amount of 4- In the cases crystals become ferromagnetic and are anisotropic. where Y is As, chlorine may be added as AsCl E l 7 The tube is slowly heated up to about 800 C., avoiding Xamp e a temperature gradient, and is maintained at this tempera- The procedure of Example 4 was repeated, replacing ture until equilibrium formation of the compound results. the selenium with a corresponding amount of tellurium. This can take approximately one day, but is not critical. Single crystals of UAsTe were produced Which, however, Then the end of the quartz tube which contains the startwere smaller (up to 5 mm. edge length and 0.5 mm. thick) ing material is heated up to l0001200 C. and the other and almost white (only slightly brassy). end maintained 50 to C. cooler. The transport tube The characteristics of the different compounds, includmay be tilted in order to accelerate flowing of the carrier mg lattice constants, are set forth in the following table:

a(A.)=|;0.003 c(A.);l=0.005 o;( K.) 0,, K.) CM (W/c a. 813 7. 981 +70 0.53 ('1 200 K. 3. 374 8.158 120 +110 0. 55 (T 150 K 25 (p) 3. 937 8.530 150 0. 68 ('l l60 K a. 961 8.178 3.986 8. 384 4.116 8.678 0. 4.167 8. 764 0 4.321 9.063 UBiTa 4.434 9.157

a, c-Lattice constants of the tetragonal UXZ compounds. (i -Ferromagnetic ordering temperature (Curie Point). 0,,-Paramagnetic Curie temperature (Weiss constant) CM-Curie constant per mole. aIhem10eleetric power near room temperature. n, pnor p-type, respectively.

I Polycrystalline sample only.

Derived from susceptibility measurements in the paramagnetic temperature range above the temperatures indicated in brackets according to the equation.

Where xM=suscept per mole.

It will be noted that the examples produce crystals of one cation only, but it is also possible to produce mixed crystals of UXZ and ThXZ as the two types of compounds have the same crystal structure. This has been verified in the case (U, Th)AsSe. However, in such a case when part of the uranium atoms are replaced a magnetic dilution results, that is to say, the magnetic moment per volume as well as the Curie temperature decrease.

I claim:

1. A compound UXZ in crystalline form in which X is selected from the group consisting of sulfur, selenium and tellurium, and Z is selected from the group consisting of phosphorus, arsenic, antimony and bismuth.

2. A compound according to claim 1 in the form of a plate-like single crystal, the crystal being metallic in appearance, white to brass colored, paramagnetic at room temperature, and ferromagnetic at temperatures below about 100 K.

3. As a new composition of matter crystalline UAsS.

4. A compound according to claim 3 in the form of a plate-like single crystal, brass colored, metallic in appearance, paramagnetic at room temperatures, being anisotropically ferromagnetic at temperatures below about 120 K.

5. As a new composition of matter crystalline UAsSe.

6. As a new composition of matter crystalline UPS.

7. As a new composition of matter crystalline UPSe.

8. As a new composition of matter crystalline USbSe.

9. As a new composition of matter crystalline USbTe.

10. A process of producing single crystals of a compound UXZ, in which X is selected from the group consisting of sulfur, selenium and tellurium, and Z is selected from the group consisting of phosphorus, arsenic, antimony and bismuth, by the halogen vapor transport system, which comprises subjecting U.X.Z powder mixture to reaction with a transport gas reaction atmosphere, where the transport gas is selected from the grou consisting of chlorine, bromine and iodine, in a vapor phase transport equipment at a temperature of about 900- 1300 C. while maintaining another zone of the transport equipment from to C. cooler until large platelike single crystals of the compound UXZ are produced in the cooler zone and recovering the crystals so produced.

References Cited Norman, L. D., Thermoelectric Properties of Depleted Uranium Selenides and Tellurides, Bureau of Mines Report 6638, 1965.

Nucloar Science Abstracts 17-14856, Uranium Chalcogenides, May 15, 1963.

Nuclear Science Abstracts 17-24064, Nuclear Fuel Element Report, July 31, 1963.

CARL D. QUARFORTH, Primary Examiner M. J. MCGREAL, Assistant Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,506,410 April 14 1970 Fritz Hulliger It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 31, "YP" should read ZP line 39, "UAaS" should read UAsS same line 39, UAaSe" should read UAsSe Column 2, line 5, "U Y should read U 2 line 39, after "0.8" insert 8 Signed and sealed this 15th day of December 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, J R. Attesting Officer 7 Commissioner of Patents 

